Multiple pitch removable blade propeller



1963 P. K- DUNCAN 3,073,395

MULTIPLE PITCH REMOVABLE BLADE PROPELLER Filed Dec. 12, 1960 INVENTOR.

j; By PAUL K. DUNCAN ATTORNEY iclnited gdtates 3,073,395 MULTEPLE PHQHREMQVABLE BLADE PRGPELLER Paui K. Duncan, 5211 SW. 7th St, Miami 44,Fla. Filed Dec. 32, less, Ser. No. 75,263 7 (Jlaims. (til. Fill-160.6)

This invention relate to improvements in marine propellets, and hasparticular reference to a multiple pitch removable blade propeller.

Marine propellers present problems with which the industry has long hadto contend. In the manufacture of the propeller there is the problem ofobtaining sufficient precision of balance and symmetry. Underconventional manufacturing methods it is difliculit to ob tain gooddynamic balance in the masses of two or three blades on a common hub. Itis also diflicult to make all the blades sufficiently identical incontour and thick mess that they will react exactly the same in thewater, particularly in high speed rotation. Either lack of dynamicbalance or differences in the blade reactions in the water createobjectionable vibration at high speed. The high degree of accuracynecessary to eliminate such vibration normally requires considerablehand work which makes the propellers quite expensive under conventionalmethods.

There also exists the problem of repair of minor damage after thepropeller is put into service. Small nicks and dents in the blades, forexample, are often removed 7 by hammering or filing. In the former casethere may be no Weight unbalance, but, nevertheless, the repaired bladecan seldom be restored so perfectly that it will not present a difierentreaction in the water. In the latter case both balance and Waterreaction are disturbed, making it very difiicult to eliminate vibrationin the repaired propeller.

The primary object of the present invention is, therefore, to provide animproved propeller having removable blades which are precisely identicalto each other so that exact balance and uniformity of water reaction areobtained in the blades of a new propeller and so that blades damaged inuse can be replaced individually without replacing the whole propelleror attempting repair.

Further objects are to provide a propeller in which all the blades arederived from a single mold, to provide a propeller of the type describedin which the blades may be either of cast metal or molded plastic, toprovide an improved propeller blade which will draw from an injectionmold, to provide a novel and improved pitch adjustment for the blades,and to provide improved means for securing the blades on the hub tofacilitate pitch adjustment, removal and replacement.

The present form of construction permits the hub and blades to be madeof dilferent materials, if desired. The hub would ordinarily be made ofmetal such as steel or bronze, while the blades may be made from avariety of materials such as plastic, die cast aluminum, zinc, potmetal, or other alloys. Each blade has a beveled circular base to fitthe semicircular forward end of a dovetail slot on one side of the hub.The base is rotatable in the slot for pitch adjutment, which adjustmentis positively locked by peripheral notches in the base engageable with apin in the slot. Each blade base is secured in its hub slot by adovetail slide lock having a semicircular end to lit the blade base. Theslide locks for all the blades are secured by a ring nut on the rear endof the hub. This form of construction makes it easy to change the pitchwhen desired and to replace a damaged blade. The individual blades canbe made so inexpensively that it is more economical to carry spareblades than to attempt repair of a damaged blade.

Patented Jan. 15, 1963 ice Additional objects and advantages will becomeapparent and the invention will be better understood from the followingdescription of the preferred embodiment illustrated in the accompanyingdrawing. Various changes may be made, however, in thedetails ofconstruction and arrangement of par-ts and certain features may be usedwithout others. All such modifications within the scope of the appendedclaims are included in the invention.

In the drawings:

FIGURE 1 is an exploded view of a propeller embodying the features ofthe invention showing one blade removed from the hub;

FIGURE 2 is a side elevation view of the propeller of FIGURE 1; and

FIGURE 3 is a longitudinal sectional View on the line 3-3 of FIGURE 2.

In FIGURE 1 the propeller is seen to comprise a hub lit having a shaftbore 9 and a pair of identical blades 1'1 and 12;, each with a circularbase 13. Each blade is secured to the hub by a dovetail slide lock 14,the slide locks in turn being secured by a ring nut 15. The hub may alsobe made to mount three or four blades if desired. I

The hub is provided with a flat chordal surface 20 for each blade. Thisflat surface contains a dovetail groove or slot 21 having an entranceopening at the rear end or the hub and a closed semicircular forward end22 The sides of circular base 13 are beveled at an angle to fit thesides and end of slot 21 as shown, whereby the base will rotate in theslot to provide the desired pitch angle for the blade, the blade beingrotatable through a full circ e in the slot 21. A selected pitchadjustment is retained by a plurality ofradial notches 25 in thecircular base 13 which are engageable with a pin 26 in the semicircularend 22 of the slot, the pin being radial to the axis of the hub. Thenotches '25 provide for different forward speeds including a slowtrolling speed and may include neutral and reverse positions, ifdesired.

Projecting from the rear end of the hub is an externally threaded boss27 concentric with the axis of the hub and of slightly less radius thanthe distance from the flat bottom of slot 21 to the axis of the hub. Thepropeller is assembled by sliding each blade base13 into its slot 21.The top or outer side of the blade base 13 is provided with an indexmark 30, and the fiat surface 20 is provided with reference marks 31designating dilferent pitch edges. By turning the index mark 30 to aselected one of the reference marks 3-1, the blade is set at the desiredpitch. Then the blade base is pushed into the end of slot 21 to engagelocking pin 26 in one of the notches '25, after which the blade will nolonger rotate in slot 21. Slide locks 14 are then inserted in slots 21and ring nut 15 is applied to the boss 27.

Each slide lock has a semicircular inner end 35 beveled to the sameangle as blade base 13 and clamping the half 'of the periphery of thebase that is not clamped by I beveled slot end 22. The outer ends ofslide locks 14 project slightly beyond the ends of slots 21 whereby thering nut bears against the ends of slide locks in spaced relation to theend surface 32 of the hub to clamp the blade bases 13 securely in theends of slots 21. Suitable lock means may be provided for ring nut 15,if desired.

When it is desired to change the pitch of the blades, it is necessaryonly to loosen the ring nut 15 so that the blade bases 13 will moverearwardly a fraction of an inch to clear locking pins 26. Then theblades may be rotated to turn the index mark 30 to a different one ofthe marks 31 without removing any of the parts. When a blade is to bereplaced, both the ring nut and slide lock are removed as shown inFIGURE 1. It is not necessary to disturb the hub mounting on thepropeller shaft.

Ring nut 15 may be withdrawn'over a nut on the end of the propellershaft since the latter need be only of sufficient diameter to engage theend surface 36 of boss 27 within the thread diameter of the boss.

Since the blades are all made individually in the same mold, it isevident that they will be exactly identical and precisely balanced inall respects without the necessity for any hand work. The blades can bemolded or. cast so inexpensively, and the blades can be changed soeasily, that there is no necessity for attempting to repair a damagedblade. Thus, the present improved form of construction solves not onlycertain serious manufacturing problems, but also the major repair andmaintenance problems for the user.

Having now described my invention and in what manner the same may beused, what I claim as new and desire to protect by Letters Patent is:

1. A propeller comprising a hub having a plurality of longitudinal slotsin its outer peripheral surface, blades having circular bases rotatablein said slots for pitch adjustment, slide locks in said slots havingsemicircular inner ends clamping said blade bases in end portions ofsaid slots, and a nut coaxial on said hub clamping all of said slidelocks against said blade bases.

2. A propeller comprising a hub having a plurality of longitudinal slotsin its outer peripheral surface, blades having circular bases rotatablein said slots for pitch adjustment, means in said slots locking saidblade bases against rotation, slide locks in said slots havingsemicircular inner ends clamping said blade bases in end portions ofsaid slots and a nut coaxial on said hub clamping all of said slidelocks against said blade bases.

3. A propeller comprising a hub having a plurality of longitudinalsurface slots with closed forward ends and open rear ends, an axialcylindrical boss on the rear end of said hub having an external screwthread, said hub having an axial bore therethrough to receive apropeller shaft, an annular end surface on said boss between said boreand said thread, propeller blades mounted in said slots, slide locks insaid slots clamping said blades against said closed forward ends of theslots, and a ring nut on said boss clamping said slide locks againstsaid blades.

4. A propeller comprising a hub having a plurality of longitudinal.dovetail slots each having a semicircular closed end and an open end,blades having beveled circular bases rotatable in said slots for pitchadjustment and fitting said semicircular ends of said slots, beveledslide locks in said slots having beveled semicircular ends fitting saidblade bases, and means clamping said slide locks against said bladebases.

5. A propeller comprising a hub having a plurality of longitudinaldovetail slots each having a semicircular closed end and an open end,blades having beveled circular bases rotatable in said slots for pitchadjustment and fitting said semicircular ends of said slots, beveledslide locks in said slots having beveled semicircular ends fitting saidblade bases, means locking said blade bases in rotative adjustment, anda nut on said hub clamping said slide locks against said blade bases,said blade bases be ing disengageable from said locking means for pitchadjustment when said nut is loosened.

6. A propeller comprising a hub having a plurality of longitudinaldovetail slots each having a semicircular closed end and an open end,blades having beveled and notched circular bases rotatable in said slotsfor pitch adjustment and fitting said semicircular ends of said slots,pins in said semicircular slot ends engaging .said base notches to locksaid pitch adjustment, beveled slide locks in said slots having beveledsemicircular ends fitting said blade bases, and a out on said hubclamping said slide locks against said blade bases.

7. A propeller comprising a hub having a plurality of longitudinaldovetail slots each having a semicircular closed end and an open end,blades having beveled and notched circular bases rotatable in said slotsfor pitch adjustment and fitting said semicircular ends of said slots,means in said slots engaging said base notches to lock said pitchadjustment, beveled slide locks in said slots having beveledsemicircular ends fitting said blade bases, and a single means clampingall of said slide locks against said blade bases.

References Cited in the file of this patent UNITED STATES PATENTS1,010,929 Loetzer Dec. 5, 1911 1,634,329 Malm July 5, 1927 1,819,728Bough Aug. 18, 1931 2,664,961 Goede Jan. 5, 1954 2,844,207 Curley July22, 1958 FOREIGN PATENTS 546,799 Germany Mar. 16, 1932 1,128,113 FranceApr. 20, 1956

1. A PROPELLER COMPRISING A HUB HAVING A PLURALITY OF LONGITUDINAL SLOTSIN ITS OUTER PERIPHERAL SURFACE, BLADES HAVING CIRCULAR BASES ROTATABLEIN SAID SLOTS FOR PITCH ADJUSTMENT, SLIDE LOCKS IN SAID SLOTS HAVINGSEMICIRCULAR INNER ENDS CLAMPING SAID BLADE BASES IN END PORTIONS OFSAID SLOTS, AND A NUT COAXIAL ON SAID HUB CLAMPING ALL OF SAID SLIDELOCKS AGAINST SAID BLADE BASES.